1. Field of the Invention
The present invention relates to optical guiding devices, particularly, to an optical guiding device guiding at least a laser beam, and backlight modules using the optical guiding device.
2. Discussion of the Related Art
In a liquid crystal display device (LCD device), a liquid crystal is a substance that does not illuminate light by itself. Instead, the liquid crystal propagates (transmits) light received from a light source to display information. In the case of a typical liquid crystal display device, a backlight module powered by electricity supplies the needed light.
With the development of LCD technology, large-size LCD devices have been actively sought and researched. The larger the backlight modules, the higher the power consumption and the materials needed. To minimize the power consumption of the larger LCD devices, the backlight module of the larger LCD devices would usually employ fewer light sources. However, decreasing the light sources would decrease the optical performance of the backlight module, such as brightness, light output uniformity, and so on. Thus, affecting the display performance of the large-size LCD. Typically, backlight modules are classified into an edge lighting type or a bottom lighting type based upon the position of the light sources in the LCD devices. By employing the edge lighting type backlight module allows the LCD to adopt a thinner width, most of the large-size LCD devices employ the edge lighting type backlight module.
Referring to FIG. 13, a typical edge lighting type backlight module 100 includes two cold cathode fluorescence lamps (CCFLs) 11, a light guide plate 12, a plurality of complementary optical elements 13, a light reflective sheet 14, a receiving frame 15 and a bottom frame 16. The two CCFLs 11 are disposed adjacent to two opposite side surfaces of the light guide plate 12. The optical elements 13 include a first light diffusion sheet 131, a prism sheet 132, and a second diffusion sheet 133 stacked on the light guide plate 12 in that order. The light reflective sheet 14 is positioned under the light guide plate 12. The receiving frame 15 and the bottom frame 16 cooperatively form a receiving space. The CCFLs 11, the light guide plate 12, the optical elements 13 and the light reflective sheet 14, are assembled in the receiving space together.
Generally, an optical efficiency of a CCFL is relatively high, however, the volume of the CCFL is large and the power consumption of the CCFL is high. Furthermore, CCFL only covers about 75 percent of color saturation as defined by the National Television Standards Committee (NTSC). Therefore, the CCFL cannot satisfy high quality liquid crystal display requirements.
What is needed, therefore, is a new backlight module that overcomes the above mentioned disadvantages.